[18F]FPRGD2 PET/CT imaging of integrin αvβ3 levels in patients with locally advanced rectal carcinoma
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Our primary objective was to determine if [18F]FPRGD2 PET/CT performed at baseline and/or after chemoradiotherapy (CRT) could predict tumour regression grade (TRG) in locally advanced rectal cancer (LARC). Secondary objectives were to compare baseline [18F]FPRGD2 and [18F]FDG uptake, to evaluate the correlation between posttreatment [18F]FPRGD2 uptake and tumour microvessel density (MVD) and to determine if [18F]FPRGD2 and FDG PET/CT could predict disease-free survival.
Baseline [18F]FPRGD2 and FDG PET/CT were performed in 32 consecutive patients (23 men, 9 women; mean age 63 ± 8 years) with LARC before starting any therapy. A posttreatment [18F]FPRGD2 PET/CT scan was performed in 24 patients after the end of CRT (median interval 7 weeks, range 3 – 15 weeks) and before surgery (median interval 4 days, range 1 – 15 days).
All LARC showed uptake of both [18F]FPRGD2 (SUVmax 5.4 ± 1.5, range 2.7 – 9) and FDG (SUVmax 16.5 ± 8, range 7.1 – 36.5). There was a moderate positive correlation between [18F]FPRGD2 and FDG SUVmax (Pearson’s r = 0.49, p = 0.0026). There was a moderate negative correlation between baseline [18F]FPRGD2 SUVmax and the TRG (Spearman’s r = −0.37, p = 0.037), and a [18F]FPRGD2 SUVmax of >5.6 identified all patients with a complete response (TRG 0; AUC 0.84, 95 % CI 0.68 - 1, p = 0.029). In the 24 patients who underwent a posttreatment [18F]FPRGD2 PET/CT scan the response index, calculated as [(SUVmax1 − SUVmax2)/SUVmax1] × 100 %, was not associated with TRG. Post-treatment [18F]FPRGD2 uptake was not correlated with tumour MVD. Neither [18F]FPRGD2 nor FDG uptake predicted disease-free survival.
Baseline [18F]FPRGD2 uptake was correlated with the pathological response in patients with LARC treated with CRT. However, the specificity was too low to consider its clinical routine use.
KeywordsRGD PET Rectal cancer Integrin Angiogenesis
We thank the operators and Christine Mella (CYCLOTRON Research Centre), the technologists (Nuclear Medicine division), Isabelle Jupsin (Oncology Department), Kamilia Elkandoussi and Agnès Delga (Biobank, Pathology Department), Fabienne Perin (GIGA-Research, Laboratory of Tumour and Developmental Biology), Estelle Dortu and Chantal Humblet (GIGA-Research, Cytology and Histology Department), Laurence Seidel (Biostatistics Department) and Marcella Chavez (coordination of Translational Research in Oncology). Preliminary results were presented (as a poster) at the 2012 SNMMI Annual Meeting (Miami, Florida, US).
Compliance with ethical standards
The Belgian Fondation contre le Cancer and the federal Ministry of Health (Plan Cancer) supported the trial.
Conflicts of interest
The institutional Committee on Ethics approved the present prospective study protocol registered in the European Clinical Trials Database (EudraCT) under the reference number 2010-019219-39.
Every patient provided signed written informed consent.
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